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  • Learning AES: the KeyBytes

    - by Tom Brito
    I got the following example from here: import java.security.Security; import javax.crypto.Cipher; import javax.crypto.spec.SecretKeySpec; public class MainClass { public static void main(String[] args) throws Exception { Security.addProvider(new org.bouncycastle.jce.provider.BouncyCastleProvider()); byte[] input = "www.java2s.com".getBytes(); byte[] keyBytes = new byte[] { 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f, 0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17 }; SecretKeySpec key = new SecretKeySpec(keyBytes, "AES"); Cipher cipher = Cipher.getInstance("AES/ECB/PKCS7Padding", "BC"); System.out.println(new String(input)); // encryption pass cipher.init(Cipher.ENCRYPT_MODE, key); byte[] cipherText = new byte[cipher.getOutputSize(input.length)]; int ctLength = cipher.update(input, 0, input.length, cipherText, 0); ctLength += cipher.doFinal(cipherText, ctLength); System.out.println(new String(cipherText)); System.out.println(ctLength); // decryption pass cipher.init(Cipher.DECRYPT_MODE, key); byte[] plainText = new byte[cipher.getOutputSize(ctLength)]; int ptLength = cipher.update(cipherText, 0, ctLength, plainText, 0); ptLength += cipher.doFinal(plainText, ptLength); System.out.println(new String(plainText)); System.out.println(ptLength); } } I imagine that the byte[] keyBytes should be random generated, so I gone to test the max size before do it. When adding one more byte 0x18 to the array, the exception raised: InvalidKeyException: Key length not 128/192/256 bits. But the original 18 bytes (from 0 to 17) are not multiple of nither 128, 192 or 256. I would like to understand the math here.. can anyone explain me? Thanks!

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  • Visual Studio Web Application edit source while running like in Tomcat\Eclipse\Java

    - by Bryan Migliorisi
    In an ASP.NET Web Site project, I've always been able to make changes to the underlying C# code and simply refresh the page in the browser and my changes would be there instantly. I can do the same thing when working with Java and Eclipse - edit my Java source and refresh the page and my changes are there. I cannot do this in ASP.NET MVC though and it is a real downer - I have to stop the running process and make my changes, and then restart debugging. This is a huge waste of time. Am I doing it wrong? What is the best approach to ASP.NET MVC development?

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  • web service - client classes

    - by Noona
    The web service that I implemented is up and running, when I try to run the client I get the following error with regard to the classes that were generated using wsimport, Caused by: java.security.PrivilegedActionException: com.sun.xml.internal.bind.v2.runtime.IllegalAnnotationsException: 4 counts of IllegalAnnotationExceptions Two classes have the same XML type name "{http://server.agency.hw2/}userJoined". Use @XmlType.name and @XmlType.namespace to assign different names to them. this problem is related to the following location: at hw2.chat.backend.main.generatedfromserver.UserJoined at public javax.xml.bind.JAXBElement hw2.chat.backend.main.generatedfromserver.ObjectFactory.createUserJoined(hw2.chat.backend.main.generatedfromserver.UserJoined) at hw2.chat.backend.main.generatedfromserver.ObjectFactory this problem is related to the following location: at ChatCompany.BackendChatServer.hw2.chat.backend.main.generatedfromserver.UserJoined Two classes have the same XML type name "{http://server.agency.hw2/}userJoinedResponse". Use @XmlType.name and @XmlType.namespace to assign different names to them. this problem is related to the following location: at hw2.chat.backend.main.generatedfromserver.UserJoinedResponse at public javax.xml.bind.JAXBElement hw2.chat.backend.main.generatedfromserver.ObjectFactory.createUserJoinedResponse(hw2.chat.backend.main.generatedfromserver.UserJoinedResponse) But I can't figure out what exactly is meant by the error. I am assuming I need to change something in annotations in this class as pointed out by the compiler: @XmlAccessorType(XmlAccessType.FIELD) @XmlType(name = "userJoinedResponse") public class UserJoinedResponse { } could someone please point out why there's a name collision and what annotations I need to change? thanks

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  • How to use XPath to filter elements by TextContent? get parent by axis?

    - by Michael Mao
    Hi all: I've found a similar question on SO, however, that seems not exactly what I wanna achieve: Say, this is a sample XML file: <root> <item> <id isInStock="true">10001</id> <category>Loose Balloon</category> </item> <item> <id isInStock="true">10001</id> <category>Bouquet Balloon</category> </item> <item> <id isInStock="true">10001</id> <category>Loose Balloon</category> </item> </root> If I wanna get a "filtered" subset of the item elements from this XML, how could I use an XPath expression to directly address that? XPathExpression expr = xpath.compile("/root/item/category/text()"); I now know this would evaluate to be the collection of all the TextContent from the categories, however, that means I have to use a collection to store the values, then iterate, then go back to grab other related info such as the item id again. Another question is : how could I refer to the parent node properly? Say, this xpath expression would get me the collection of all the id nodes, right? But what I want is the collection of item nodes: XPathExpression expr = xpath.compile("/root/item/id[@isInStock='true']"); I know I should use the "parent" axis to refer to that, but I just cannot make it right... Is there a better way of doing this sort of thing? Learning the w3cschools tutorials now... Sorry I am new to XPath in Java, and thanks a lot in advance.

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  • How can I filter a JTable?

    - by Jonas
    I would like to filter a JTable, but I don't understand how I can do it. I have read How to Use Tables - Sorting and Filtering and I have tried with the code below, but with that filter, no rows at all is shown in my table. And I don't understand what column it is filtered on. private void myFilter() { RowFilter<MyModel, Object> rf = null; try { rf = RowFilter.regexFilter(filterFld.getText(), 0); } catch (java.util.regex.PatternSyntaxException e) { return; } sorter.setRowFilter(rf); } MyModel has three columns, the first two are strings and the last column is of type Integer. How can I apply the filter above, consider the text in filterFld.getText() and only filter the rows where the text is matched on the second column? I would like to show all rows that starts with the text specified by filterFld.getText(). I.e. if the text is APP then the JTable should contain the rows where the second column starts with APPLE, APPLICATION but not the rows where the second column is CAR, ORANGE. I have also tried with this filter: RowFilter<MyModel, Integer> itemFilter = new RowFilter<MyModel, Integer>(){ public boolean include(Entry<? extends MyModel, ? extends Integer> entry){ MyModel model = entry.getModel(); MyItem item = model.getRecord(entry.getIdentifier()); if (item.getSecondColumn().startsWith("APP")) { return true; } else { return false; } } }; How can I write a filter that is filtering the JTable on the second column, specified by my textfield?

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  • Detecting Asymptotes in a Graph

    - by nasufara
    I am creating a graphing calculator in Java as a project for my programming class. There are two main components to this calculator: the graph itself, which draws the line(s), and the equation evaluator, which takes in an equation as a String and... well, evaluates it. To create the line, I create a Path2D.Double instance, and loop through the points on the line. To do this, I calculate as many points as the graph is wide (e.g. if the graph itself is 500px wide, I calculate 500 points), and then scale it to the window of the graph. Now, this works perfectly for most any line. However, it does not when dealing with asymptotes. If, when calculating points, the graph encounters a domain error (such as 1/0), the graph closes the shape in the Path2D.Double instance and starts a new line, so that the line looks mathematically correct. Example: However, because of the way it scales, sometimes it is rendered correctly, sometimes it isn't. When it isn't, the actual asymptotic line is shown, because within those 500 points, it skipped over x = 2.0 in the equation 1 / (x-2), and only did x = 1.98 and x = 2.04, which are perfectly valid in that equation. Example: In that case, I increased the window on the left and right one unit each. My question is: Is there a way to deal with asymptotes using this method of scaling so that the resulting line looks mathematically correct? I myself have thought of implementing a binary search-esque method, where, if it finds that it calculates one point, and then the next point is wildly far away from the last point, it searches in between those points for a domain error. I had trouble figuring out how to make it work in practice, however. Thank you for any help you may give!

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  • Can a GeneralPath be modified?

    - by Dov
    java2d is fairly expressive, but requires constructing lots of objects. In contrast, the older API would let you call methods to draw various shapes, but lacks all the new features like transparency, stroke, etc. Java has fairly high costs associated with object creation. For speed, I would like to create a GeneralPath whose structure does not change, but go in and change the x,y points inside. path = new GeneralPath(GeneralPath.WIND_EVEN_ODD, 10); path.moveTo(x,y); path.lineTo(x2, y2); double len = Math.sqrt((x2-x)*(x2-x) + (y2-y)*(y2-y)); double dx = (x-x2) * headLen / len; double dy = (y-y2) * headLen / len; double dx2 = -dy * (headWidth/headLen); double dy2 = dx * (headWidth/headLen); path.lineTo(x2 + dx + dx2, y2 + dy + dy2); path.moveTo(x2 + dx - dx2, y2 + dy - dy2); path.lineTo(x2,y2); This one isn't even that long. Imagine a much longer sequence of commands, and only the ones on the end are changing. I just want to be able to overwrite commands, to have an iterator effectively. Does that exist?

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  • Android: NullPointerException error in getting data in database

    - by Gil Viernes Marcelo
    This what happens in the system. 1. Admin login this is in other activity but i will not post it coz it has nothing to do with this (no problem) 2. Register user in system (using database no problem) 3. Click add user button (where existing user who register must display its name in ListView) Problem: When I click adduser to see if the system registered the user, it force close. CurrentUser.java package com.example.istronggyminstructor; import java.util.ArrayList; import android.os.Bundle; import android.app.Activity; import android.content.Context; import android.content.Intent; import android.database.Cursor; import android.view.Gravity; import android.view.LayoutInflater; import android.view.Menu; import android.view.View; import android.view.View.OnClickListener; import android.view.ViewGroup; import android.view.ViewGroup.LayoutParams; import android.view.WindowManager; import android.widget.ArrayAdapter; import android.widget.Button; import android.widget.EditText; import android.widget.FrameLayout; import android.widget.ListView; import android.widget.PopupWindow; import android.widget.TextView; import android.widget.Toast; import java.util.ArrayList; import java.util.List; import java.util.Random; import com.example.istronggyminstructor.registeredUserList.Users; import android.content.ContentValues; import android.database.Cursor; import android.database.SQLException; import android.database.sqlite.SQLiteDatabase; public class CurrentUsers extends Activity { private Button register; private Button adduser; EditText getusertext, getpass, getweight, textdisp; View popupview, popupview2; public static ArrayList<String> ArrayofName = new ArrayList<String>(); protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_current_users); register = (Button) findViewById(R.id.regbut); adduser = (Button) findViewById(R.id.addbut); register.setOnClickListener(new OnClickListener() { @Override public void onClick(View arg0) { LayoutInflater inflator = (LayoutInflater) getBaseContext() .getSystemService(LAYOUT_INFLATER_SERVICE); popupview = inflator.inflate(R.layout.popup, null); final PopupWindow popupWindow = new PopupWindow(popupview, LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT); popupWindow.showAtLocation(popupview, Gravity.CENTER, 0, 0); popupWindow.setFocusable(true); popupWindow.update(); Button dismissbtn = (Button) popupview.findViewById(R.id.close); dismissbtn.setOnClickListener(new OnClickListener() { @Override public void onClick(View arg0) { popupWindow.dismiss(); } }); popupWindow.showAsDropDown(register, 50, -30); } }); //Thread.setDefaultUncaughtExceptionHandler(new forceclose(this)); } public void registerUser(View v) { EditText username = (EditText) popupview.findViewById(R.id.usertext); EditText password = (EditText) popupview .findViewById(R.id.passwordtext); EditText weight = (EditText) popupview.findViewById(R.id.weight); String getUsername = username.getText().toString(); String getPassword = password.getText().toString(); String getWeight = weight.getText().toString(); dataHandler dbHandler = new dataHandler(this, null, null, 1); Users user = new Users(getUsername, getPassword, Integer.parseInt(getWeight)); dbHandler.addUsers(user); Toast.makeText(getApplicationContext(), "Registering...", Toast.LENGTH_SHORT).show(); } public void onClick_addUser(View v) { LayoutInflater inflator = (LayoutInflater) getBaseContext() .getSystemService(LAYOUT_INFLATER_SERVICE); popupview2 = inflator.inflate(R.layout.popup2, null); final PopupWindow popupWindow = new PopupWindow(popupview2, LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT); popupWindow.showAtLocation(popupview2, Gravity.CENTER, 0, -10); popupWindow.setFocusable(true); popupWindow.update(); Button dismissbtn = (Button) popupview2.findViewById(R.id.close2); dismissbtn.setOnClickListener(new OnClickListener() { @Override public void onClick(View arg0) { popupWindow.dismiss(); } }); popupWindow.showAsDropDown(register, 50, -30); dataHandler dbHandler = new dataHandler(this, null, null, 1); dbHandler.getAllUsers(); ListView list = (ListView)findViewById(R.layout.popup2); ArrayAdapter<String> adapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, ArrayofName); list.setAdapter(adapter); } @Override public boolean onCreateOptionsMenu(Menu menu) { getMenuInflater().inflate(R.menu.current_users, menu); return true; } } registeredUserList.java package com.example.istronggyminstructor; public class registeredUserList { public static class Users { private static int _id; private static String _users; private static String _password; private static int _weight; private static String[] _workoutlists; private static int _score; public Users() { } public Users(String username, String password, int weight) { _users = username; _password = password; _weight = weight; } public int getId() { return _id; } public static void setId(int id) { _id = id; } public String getUsers() { return _users; } public static void setUsers(String users) { _users = users; } public String getPassword(){ return _password; } public void setPassword(String password){ _password = password; } public int getWeight(){ return _weight; } public static void setWeight(int weight){ _weight = weight; } public String[] getWorkoutLists(){ return _workoutlists; } public void setWorkoutLists(String[] workoutlists){ _workoutlists = workoutlists; } public int score(){ return _score; } public void score(int score){ _score = score; } } } dataHandler.java package com.example.istronggyminstructor; import java.util.ArrayList; import java.util.List; import com.example.istronggyminstructor.registeredUserList.Users; import android.content.ContentValues; import android.content.Context; import android.database.Cursor; import android.database.sqlite.SQLiteDatabase; import android.database.sqlite.SQLiteDatabase.CursorFactory; import android.database.sqlite.SQLiteOpenHelper; public class dataHandler extends SQLiteOpenHelper { private static final int DATABASE_VERSION = 1; private static final String DATABASE_NAME = "userInfo.db"; public static final String TABLE_USERINFO = "user"; public static final String COLUMN_ID = "_id"; public static final String COLUMN_USERNAME = "username"; public static final String COLUMN_PASSWORD = "password"; public static final String COLUMN_WEIGHT = "weight"; public dataHandler(Context context, String name, CursorFactory factory, int version) { super(context, DATABASE_NAME, factory, DATABASE_VERSION); } @Override public void onCreate(SQLiteDatabase db) { String CREATE_USER_TABLE = "CREATE TABLE " + TABLE_USERINFO + " (" + COLUMN_ID + " INTEGER PRIMARY KEY, " + COLUMN_USERNAME + " TEXT," + COLUMN_PASSWORD + " TEXT, " + COLUMN_WEIGHT + " INTEGER " + ");"; db.execSQL(CREATE_USER_TABLE); } @Override public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { db.execSQL("DROP TABLE IF EXISTS " + TABLE_USERINFO); onCreate(db); } public void addUsers(Users user) { ContentValues values = new ContentValues(); values.put(COLUMN_USERNAME, user.getUsers()); values.put(COLUMN_PASSWORD, user.getPassword()); values.put(COLUMN_WEIGHT, user.getWeight()); SQLiteDatabase db = this.getWritableDatabase(); db.insert(TABLE_USERINFO, null, values); db.close(); } public Users findUsers(String username) { String query = "Select * FROM " + TABLE_USERINFO + " WHERE " + COLUMN_USERNAME + " = \"" + username + "\""; SQLiteDatabase db = this.getWritableDatabase(); Cursor cursor = db.rawQuery(query, null); Users user = new Users(); if (cursor.moveToFirst()) { cursor.moveToFirst(); Users.setUsers(cursor.getString(1)); //Users.setWeight(Integer.parseInt(cursor.getString(3))); not yet needed cursor.close(); } else { user = null; } db.close(); return user; } public List<Users> getAllUsers(){ List<Users> user = new ArrayList(); String selectQuery = "SELECT * FROM " + TABLE_USERINFO; SQLiteDatabase db = this.getWritableDatabase(); Cursor cursor = db.rawQuery(selectQuery, null); if (cursor.moveToFirst()) { do { Users users = new Users(); users.setUsers(cursor.getString(1)); String name = cursor.getString(1); CurrentUsers.ArrayofName.add(name); // Adding contact to list user.add(users); } while (cursor.moveToNext()); } // return user list return user; } public boolean deleteUsers(String username) { boolean result = false; String query = "Select * FROM " + TABLE_USERINFO + " WHERE " + COLUMN_USERNAME + " = \"" + username + "\""; SQLiteDatabase db = this.getWritableDatabase(); Cursor cursor = db.rawQuery(query, null); Users user = new Users(); if (cursor.moveToFirst()) { Users.setId(Integer.parseInt(cursor.getString(0))); db.delete(TABLE_USERINFO, COLUMN_ID + " = ?", new String[] { String.valueOf(user.getId()) }); cursor.close(); result = true; } db.close(); return result; } } Logcat 08-20 03:23:23.293: E/AndroidRuntime(16363): FATAL EXCEPTION: main 08-20 03:23:23.293: E/AndroidRuntime(16363): java.lang.IllegalStateException: Could not execute method of the activity 08-20 03:23:23.293: E/AndroidRuntime(16363): at android.view.View$1.onClick(View.java:3599) 08-20 03:23:23.293: E/AndroidRuntime(16363): at android.view.View.performClick(View.java:4204) 08-20 03:23:23.293: E/AndroidRuntime(16363): at android.view.View$PerformClick.run(View.java:17355) 08-20 03:23:23.293: E/AndroidRuntime(16363): at android.os.Handler.handleCallback(Handler.java:725) 08-20 03:23:23.293: E/AndroidRuntime(16363): at android.os.Handler.dispatchMessage(Handler.java:92) 08-20 03:23:23.293: E/AndroidRuntime(16363): at android.os.Looper.loop(Looper.java:137) 08-20 03:23:23.293: E/AndroidRuntime(16363): at android.app.ActivityThread.main(ActivityThread.java:5041) 08-20 03:23:23.293: E/AndroidRuntime(16363): at java.lang.reflect.Method.invokeNative(Native Method) 08-20 03:23:23.293: E/AndroidRuntime(16363): at java.lang.reflect.Method.invoke(Method.java:511) 08-20 03:23:23.293: E/AndroidRuntime(16363): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793) 08-20 03:23:23.293: E/AndroidRuntime(16363): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560) 08-20 03:23:23.293: E/AndroidRuntime(16363): at dalvik.system.NativeStart.main(Native Method) 08-20 03:23:23.293: E/AndroidRuntime(16363): Caused by: java.lang.reflect.InvocationTargetException 08-20 03:23:23.293: E/AndroidRuntime(16363): at java.lang.reflect.Method.invokeNative(Native Method) 08-20 03:23:23.293: E/AndroidRuntime(16363): at java.lang.reflect.Method.invoke(Method.java:511) 08-20 03:23:23.293: E/AndroidRuntime(16363): at android.view.View$1.onClick(View.java:3594) 08-20 03:23:23.293: E/AndroidRuntime(16363): ... 11 more 08-20 03:23:23.293: E/AndroidRuntime(16363): Caused by: java.lang.NullPointerException 08-20 03:23:23.293: E/AndroidRuntime(16363): at com.example.istronggyminstructor.CurrentUsers.onClick_addUser(CurrentUsers.java:118) 08-20 03:23:23.293: E/AndroidRuntime(16363): ... 14 more

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  • [Microsoft][ODBC Driver Manager] Data source name not found and no default driver specified - works

    - by Matt
    Hello, I am developing a java app (with odbc bridge - forgive me - the only paradox driver I have been able to obtain is the microsoft odbc driver) - which works fine while in eclipse, (and netbeans) - connecting and obtaining data from an ancient paradox 5.x database. So long as it is run from inside my IDE - it compiles and runs flawlessly. When I export it to a runable jar, suddenly [code][Microsoft][ODBC Driver Manager] Data source name not found and no default driver specified[/code] occurs. The jar is being run on the same box as my developing IDE - so I am confused about the cause. It is being run via console from a user account, as per the IDE. My connection string is "jdbc:odbc:Driver={Microsoft Paradox Driver (*.db )};DriverID=538; Fil=Paradox 5.X; DefaultDir=C:\paradox\database\location\" - obtained from connectionstrings.com - and as mentioned before, working fine while run from the IDE. The above seems to 'magically' create its own connection, avoiding the setup of a dsn - I am unsure quite how it does - but it works. The only other thing I can think that might be pertinent is that my PC is a 64bit o/s (windows server 2008). Please help, any suggestions or comments will be greatly appreciated. Thanks, Matt

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  • Reordering arguments using recursion (pro, cons, alternatives)

    - by polygenelubricants
    I find that I often make a recursive call just to reorder arguments. For example, here's my solution for endOther from codingbat.com: Given two strings, return true if either of the strings appears at the very end of the other string, ignoring upper/lower case differences (in other words, the computation should not be "case sensitive"). Note: str.toLowerCase() returns the lowercase version of a string. public boolean endOther(String a, String b) { return a.length() < b.length() ? endOther(b, a) : a.toLowerCase().endsWith(b.toLowerCase()); } I'm very comfortable with recursions, but I can certainly understand why some perhaps would object to it. There are two obvious alternatives to this recursion technique: Swap a and b traditionally public boolean endOther(String a, String b) { if (a.length() < b.length()) { String t = a; a = b; b = t; } return a.toLowerCase().endsWith(b.toLowerCase()); } Not convenient in a language like Java that doesn't pass by reference Lots of code just to do a simple operation An extra if statement breaks the "flow" Repeat code public boolean endOther(String a, String b) { return (a.length() < b.length()) ? b.toLowerCase().endsWith(a.toLowerCase()) : a.toLowerCase().endsWith(b.toLowerCase()); } Explicit symmetry may be a nice thing (or not?) Bad idea unless the repeated code is very simple ...though in this case you can get rid of the ternary and just || the two expressions So my questions are: Is there a name for these 3 techniques? (Are there more?) Is there a name for what they achieve? (e.g. "parameter normalization", perhaps?) Are there official recommendations on which technique to use (when)? What are other pros/cons that I may have missed?

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  • text-area-text-to-be-split-with-conditions repeated

    - by desmiserables
    I have a text area wherein i have limited the user from entering more that 15 characters in one line as I want to get the free flow text separated into substrings of max limit 15 characters and assign each line an order number. This is what I was doing in my java class: int interval = 15; items = new ArrayList(); TextItem item = null; for (int i = 0; i < text.length(); i = i + interval) { item = new TextItem (); item.setOrder(i); if (i + interval < text.length()) { item.setSubText(text.substring(i, i + interval)); items.add(item); } else { item.setSubText(text.substring(i)); items.add(item); } } Now it works properly unless the user presses the enter key. Whenever the user presses the enter key I want to make that line as a new item having only that part as the subText. I can check whether my text.substring(i, i + interval) contains any "\n" and split till there but the problem is to get the remaining characters after "\n" till next 15 or till next "\n" and set proper order and subText.

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  • Backreferences in lookbehind

    - by polygenelubricants
    Can you use backreferences in a lookbehind? Let's say I want to split wherever behind me a character is repeated twice. String REGEX1 = "(?<=(.)\\1)"; // DOESN'T WORK! String REGEX2 = "(?<=(?=(.)\\1)..)"; // WORKS! System.out.println(java.util.Arrays.toString( "Bazooka killed the poor aardvark (yummy!)" .split(REGEX2) )); // prints "[Bazoo, ka kill, ed the poo, r aa, rdvark (yumm, y!)]" Using REGEX2 (where the backreference is in a lookahead nested inside a lookbehind) works, but REGEX1 gives this error at run-time: Look-behind group does not have an obvious maximum length near index 8 (?<=(.)\1) ^ This sort of make sense, I suppose, because in general the backreference can capture a string of any length (if the regex compiler is a bit smarter, though, it could determine that \1 is (.) in this case, and therefore has a finite length). So is there a way to use a backreference in a lookbehind? And if there isn't, can you always work around it using this nested lookahead? Are there other commonly-used techniques?

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  • I need an abstract field !

    - by Jules Olléon
    I know abstract fields do not exist in java. I also read this question but the solutions proposed won't solve my problem. Maybe there is no solution, but it's worth asking :) Problem I have an abstract class that does an operation in the constructor depending on the value of one of its fields. The problem is that the value of this field will change depending on the subclass. How can I do so that the operation is done on the value of the field redefined by the subclass ? If I just "override" the field in the subclass the operation is done on the value of the field in the abstract class. I'm open to any solution that would ensure that the operation will be done during the instantiation of the subclass (ie putting the operation in a method called by each subclass in the constructor is not a valid solution, because someone might extend the abstract class and forget to call the method). Also, I don't want to give the value of the field as an argument of the constructor. Is there any solution to do that, or should I just change my design ?

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  • Log4j Relative Path to Tomcat7 Log Directory File Not Found

    - by Nik
    I have this log4j XML file: <log4j:configuration xmlns:log4j="http://jakarta.apache.org/log4j/"> <appender name="gemFile" class="org.apache.log4j.RollingFileAppender"> <param name="File" value="file:${catalina.home}/logs/GEM.log" /> <param name="MaxBackupIndex" value="5" /> <param name="MaxFileSize" value="3MB" /> <param name="Append" value="true" /> <layout class="org.apache.log4j.PatternLayout"> <param name="ConversionPattern" value="[%t] %d{yyyy-MM-dd HH:mm:ss.SSS} %-5p %c{1} - %m%n" /> </layout> </appender> <root> <priority value ="info" /> <appender-ref ref="gemFile" /> </root> </log4j:configuration> ${catalina.home} resolves to C:\Apps\Apache\Tomcat7. When I deploy my WAR file, I get log4j:ERROR setFile(null,true) call failed. java.io.FileNotFoundException: file:C:\Apps\Apache\Tomcat7\logs\GEM.log (The filename, directory name, or volume label syntax is incorrect) stack trace... It is true that the log file does not exist (the folder structure does), but if I set the file directly to that path (<param name="File" value="C:/Apps/Apache/Tomcat7/logs/GEM.log" />) it works fine. Why can't I use the replacement string?

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  • executing stored procedure from Spring-Hibernate using Annotations

    - by HanuAthena
    I'm trying to execute a simple stored procedure with Spring/Hibernate using Annotations. Here are my code snippets: DAO class: public class UserDAO extends HibernateDaoSupport { public List selectUsers(final String eid){ return (List) getHibernateTemplate().execute(new HibernateCallback() { public Object doInHibernate(Session session) throws HibernateException, SQLException { Query q = session.getNamedQuery("SP_APPL_USER"); System.out.println(q); q.setString("eid", eid); return q.list(); } }); } } my entity class: @Entity @Table(name = "APPL_USER") @Inheritance(strategy = InheritanceType.SINGLE_TABLE) @DiscriminatorFormula(value = "SUBSCRIBER_IND") @DiscriminatorValue("N") @NamedQuery(name = "req.all", query = "select n from Requestor n") @org.hibernate.annotations.NamedNativeQuery(name = "SP_APPL_USER", query = "call SP_APPL_USER(?, :eid)", callable = true, readOnly = true, resultClass = Requestor.class) public class Requestor { @Id @Column(name = "EMPL_ID") public String getEmpid() { return empid; } public void setEmpid(String empid) { this.empid = empid; } @Column(name = "EMPL_FRST_NM") public String getFirstname() { return firstname; } ... } public class Test { public static void main(String[] args) { ApplicationContext ctx = new ClassPathXmlApplicationContext( "applicationContext.xml"); APFUser user = (APFUser)ctx.getBean("apfUser"); List selectUsers = user.getUserDAO().selectUsers("EMP456"); System.out.println(selectUsers); } } and the stored procedure: create or replace PROCEDURE SP_APPL_USER (p_cursor out sys_refcursor, eid in varchar2) as empId varchar2(8); fname varchar2(50); lname varchar2(50); begin empId := null; fname := null; lname := null; open p_cursor for select l.EMPL_ID, l.EMPL_FRST_NM, l.EMPL_LST_NM into empId, fname, lname from APPL_USER l where l.EMPL_ID = eid; end; If i enter invalid EID, its returning empty list which is OK. But when record is there, following exception is thrown: Exception in thread "main" org.springframework.jdbc.BadSqlGrammarException: Hibernate operation: could not execute query; bad SQL grammar [call SP_APPL_USER(?, ?)]; nested exception is java.sql.SQLException: Invalid column name Do I need to modify the entity(Requestor.class) ? How will the REFCURSOR be converted to the List? The stored procedure is expected to return more than one record.

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  • Using prepared statements with JDBCTemplate

    - by Bernhard V
    Hi. I'm using the Jdbc template and want to read from the database using prepared statements. I iterate over many lines in a csv file and on every line I execute some sql select queries with it's values. Now I want to speed up my reading from the database but I just can't get the Jdbc template to work with prepared statements. Actually I even don't know how to do it. There is the PreparedStatementCreator and the PreparedStatementCreator. As in this example both of them are created with anonymous inner classes. But inside the PreparedStatementCreator class I don't have access to the values I want to set in the prepared statement. Since I'm iterating through a csv file I can't hard code them as a String because I don't know them. I also can't pass them to the PreparedStatementCreator because there are no arguments for the constructor. I was used to the creation of prepared statements being fairly simple. Something like PreparedStatement updateSales = con.prepareStatement( "UPDATE COFFEES SET SALES = ? WHERE COF_NAME LIKE ? "); updateSales.setInt(1, 75); updateSales.setString(2, "Colombian"); updateSales.executeUpdate(): as in the Java tutorial. Your help would be very appreciated.

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  • review of a codility test - pair_sum_even_count

    - by geoaxis
    I recently took an online test on codility as part of a recruitment process. I was given two simple problems to solve in 1 hour. For those who don't know codility, its an online coding test site where you can solve ACM style problems in many different languages. if you have 30 or so mins then check this http://codility.com/demo/run/ My weapon of choice is usually Java. So on of the problems I have is as follows (I will try to remember, should have taken a screenshot) Lets say you have array A[0]=1 A[1]=-1 ....A[n]=x Then what would be the smartest way to find out the number of times when A[i]+A[j] is even where i < j So if we have {1,2,3,4,5} we have 1+3 1+5 2+4 3+5 = 4 pairs which are even The code I wrote was some thing along the lines int sum=0; for(int i=0;i<A.length-1;i++){ for (int j=i+1;j<A.length;j++){ if( ((A[i]+A[j])%2) == 0 && i<j) { sum++; } } } There was one more restriction that if the number of pairs is greater than 1e9 then it should retrun -1, but lets forget it. Can you suggest a better solution for this. The number of elements won't exceed 1e9 in normal cases. I think I got 27 points deducted for the above code (ie it's not perfect). Codility gives out a detailed assessment of what went wrong, I don't have that right now.

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  • Download MMS content on Blackberry

    - by Chris
    Hi I am relatively new to coding for the blackberry and I need to write a java application that can capture all incoming and outgoing MMS data from a Blackberry device. I have gotten the capturing of outgoing MMS's sorted with the use of A sendListener, but the problem comes with the incoming MMS's. If I use a MessageListener that processes only those of type BinaryMessage, i can capture the binary notification SMS that comes in when there is an incoming MMS. From this notification, i can get the senders MSISDN as well as the URL on the MMSC where the content is stored. To get the actual MMS content, i presume i need to download it from this URL, but im unable to get this working. I have tried just opening a HTTPConnetion to this URL, opening an inputStream on it and reading from there, but i retrieve no content. If i manually go to that URL on the blackberry, i can see the content fine (and of course the blackberry can download it automatically anyway). Can anyone please help me asap on how i can get the mms content for incoming MMS's. Thanks alot

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  • How can I place validating constraints on my method input parameters?

    - by rcampbell
    Here is the typical way of accomplishing this goal: public void myContractualMethod(final String x, final Set<String> y) { if ((x == null) || (x.isEmpty())) { throw new IllegalArgumentException("x cannot be null or empty"); } if (y == null) { throw new IllegalArgumentException("y cannot be null"); } // Now I can actually start writing purposeful // code to accomplish the goal of this method I think this solution is ugly. Your methods quickly fill up with boilerplate code checking the valid input parameters contract, obscuring the heart of the method. Here's what I'd like to have: public void myContractualMethod(@NotNull @NotEmpty final String x, @NotNull final Set<String> y) { // Now I have a clean method body that isn't obscured by // contract checking If those annotations look like JSR 303/Bean Validation Spec, it's because I borrowed them. Unfortunitely they don't seem to work this way; they are intended for annotating instance variables, then running the object through a validator. Which of the many Java design-by-contract frameworks provide the closest functionality to my "like to have" example? The exceptions that get thrown should be runtime exceptions (like IllegalArgumentExceptions) so encapsulation isn't broken.

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  • Serialization Performance and Google Android

    - by Jomanscool2
    I'm looking for advice to speed up serialization performance, specifically when using the Google Android. For a project I am working on, I am trying to relay a couple hundred objects from a server to the Android app, and am going through various stages to get the performance I need. First I tried a terrible XML parser that I hacked together using Scanner specifically for this project, and that caused unbelievably slow performance when loading the objects (~5 minutes for a 300KB file). I then moved away from that and made my classes implement Serializable and wrote the ArrayList of objects I had to a file. Reading that file into the objects the Android, with the file already downloaded mind you, was taking ~15-30 seconds for the ~100KB serialized file. I still find this completely unacceptable for an Android app, as my app requires loading the data when starting the application. I have read briefly about Externalizable and how it can increase performance, but I am not sure as to how one implements it with nested classes. Right now, I am trying to store an ArrayList of the following class, with the nested classes below it. public class MealMenu implements Serializable{ private String commonsName; private long startMillis, endMillis, modMillis; private ArrayList<Venue> venues; private String mealName; } And the Venue class: public class Venue implements Serializable{ private String name; private ArrayList<FoodItem> foodItems; } And the FoodItem class: public class FoodItem implements Serializable{ private String name; private boolean vegan; private boolean vegetarian; } IF Externalizable is the way to go to increase performance, is there any information as to how java calls the methods in the objects when you try to write it out? I am not sure if I need to implement it in the parent class, nor how I would go about serializing the nested objects within each object.

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  • Connect two client sockets

    - by Hernán Eche
    Good morning, let's say Java has two kind of sockets... server sockets "ServerSocket" client sockets or just "Socket" ////so Simple ! Imagine the situation of two processes: X Client <-- Y Server The server process Y : has a "ServerSocket", that is listening to a TCP port The client process X : send a connection request through a -client type- "Socket" X ////so Simple ! then the accept() method (in server Y) returns a new client type "Socket", when it occurs, great the two Sockets get "interconected", so the -client socket- in client process, is connected with the -client socket- in the server process then (reading/writing in socket X is like reading/writing in socket Y, and viceversa. ) TWO CLIENT SOCKETS GET INTERCONECTED!! ////so Simple ! BUT... (there is always a But..) What if I create the two CLIENT sockets in same process, and I want to get them "interconected" ? ////mmm Complex =(... even posible? Let's say how to have TWO CLIENT SOCKETS GET INTERCONECTED WITHOUT using an intermediate ServerSocket ? I 've solved it.. by creating two threads for continuously reading A and writing B, and other for reading B and writng A... but I think could be a better way..(or should!) (Those world-energy-consuming threads are not necessary with the client-server aproach) Any help or advice would be appreciated!! Thanks

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  • Cannot find symbol - variable

    - by Ben Garside
    I'm new to Java, and I'm trying to get user input, store each line of input as a variable and then return each value so that it can be passed on somewhere else. When I try and compile it is telling me that it can't find the variable magnitude. I'm assuming it won't find the others either. I'm guessing that this is because I've declare the variables inside of the "try" but don't know how to get it so that the return statement accepts them. Code is as follows: public Earthquake userAddEarthquake() { Scanner scanner = new Scanner(System.in); try{ // convert the string read from the scanner into Integer type System.out.println("Please Enter An Earthquake Magnitude: "); Double magnitude = Double.parseDouble(scanner.nextLine()); System.out.println("Please Enter The Earthquakes Latitude Position: "); scanner = new Scanner(System.in); Double positionLatitude = Double.parseDouble(scanner.nextLine()); System.out.print("Please Enter The Earthquakes Longitude Position: "); scanner = new Scanner(System.in); Double positionLongitude = Double.parseDouble(scanner.nextLine()); System.out.print("Please Enter The Year That The Earthquake Occured: "); scanner = new Scanner(System.in); int year = Integer.parseInt(scanner.nextLine()); System.out.println("Magnitude = " + magnitude); } catch(NumberFormatException ne){ System.out.println("Invalid Input"); } finally{ scanner.close(); } return new Earthquake(magnitude, positionLatitude, positionLongitude, year); }

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  • Constructing human readable sentences based on a survey

    - by Joshua
    The following is a survey given to course attendees to assess an instructor at the end of the course. Communication Skills 1. The instructor communicated course material clearly and accurately. Yes No 2. The instructor explained course objectives and learning outcomes. Yes No 3. In the event of not understanding course materials the instructor was available outside of class. Yes No 4. Was instructor feedback and grading process clear and helpful? Yes No 5. Do you feel that your oral and written skills have improved while in this course? Yes No We would like to summarize each attendees selection based on the choices chosen by him. If the provided answers were [No, No, Yes, Yes, Yes]. Then we would summarize this as "The instructor was not able to summarize course objectives and learning outcomes clearly, but was available for usually helpful outside of class. The instructor feedback and grading process was clear and helpful and I feel that my oral and written skills have improved because of this course. Based on the selections chosen by the attendee the summary would be quite different. This leads to many answers based on the choices selected and the number of such questions in the survey. The questions are usually provided by the training organization. How do you come up with a generic solution so that this can be effectively translated into a human readable form. I am looking for tools or libraries (java based), suggestions which will help me create such human readable output. I would like to hide the complexity from the end users as much as possible.

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  • NetBeans Tips and Tricks

    - by cdmckay
    I just saw an Eclipse tips & tricks post and was wondering if anyone had any tips & tricks for my IDE of choice: NetBeans. Here's a few I know and find to be useful: Removing a package: After you remove a package in NetBeans, it sticks around as a grayed-out package in your Project view. To get rid of that, switch to Files view and delete the directory. Alt-Insert (in Windows) opens up a Generate submenu at your cursor. A nice shortcut for quickly generating getters/setters (among other things). Selecting a chunk of code, right-clicking and then clicking "Refactor Introduce Method" will have NetBeans introduce a method, complete with arguments and return value. Of course you have to make sure the chunk of code only has one return value. Sometimes when you run a build and it crashes, the Java window sticks around at the bottom. I used to just click X until Windows let me End Task, but there's a nicer way to get rid of them. Click "Run Stop Build/Run" and NetBeans will close the window for you. It'll even let you close multiple applications at once. These may seem obvious to grizzled NetBeans developers, but I thought they might be useful for NetBeans newbs like me. Anyone else have any tips/tricks to share? Here are some from the comments: NetBeans allows for code templates. You can even add yours on the Code Templates tab under the Editor settings on the Options window. Some examples: Type sout and hit the tab key as a shorcut for System.out.println("") Type psvm and hit the tab key as a shorcut for public static void main(String args[]) {} Ctrl Shift C: Comments out the selected block of code. Alt Shift F: Formats the selected block of code. Ctrl E: Deletes current line. Ctrl Shift I: Fixes your imports, handy if you've just written a piece of code that needs a lot of packages imported.

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  • Determining whether geographic point is within X meters of a state border (using shapefile for borde

    - by DanM
    So I'm writing a Java app, and I've got an ESRI Shapefile which contains the borders of all the U.S. states. What I need is to be able to determine whether any given lat/lon point is within a specified distance from ANY state border line - i.e., I will not be specifying a particular border line, just need to see whether the point is close to any of them. The solution does NOT have to be very precise at all; e.g. I don't need to be dealing with measuring perpendicular to the border, or whatever. Just checking to see if going X meters north, south, east or west would result in crossing a border would be more than sufficient. The solution DOES have to be computationally efficient, as I'll be performing a huge number of these calculations. I'm planning to use the GeoTools library (though if there's a simpler option, I'm all for it) with the Shapefile plugin. What I don't really understand is: Once I've got the shapefile loaded into memory, how do I check to see whether I'm near a border? Thanks! -Dan

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